Semiconductor light emitting device

ABSTRACT

A semiconductor light emitting device includes a mount section having an insulating property connected to a heat sink, a plurality of semiconductor laser elements disposed on the mount section, and a heat radiation block having an insulating property disposed on the plurality of semiconductor laser elements. A first wiring made of a metal is disposed on an upper surface of the mount section, and a second wiring made of a metal is disposed on a lower surface of the heat radiation block, a part of the second wiring being electrically connected to the first wiring. By electrically connecting the first wiring and the second wiring to each of the plurality of semiconductor laser elements, the plurality of semiconductor laser elements are connected in series, and have a same polarity with each other at a side that each of the plurality of semiconductor laser elements is connected to the first wiring.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/986,153 filed on May 22, 2018, which is a continuation of the PCTInternational Application No. PCT/JP2016/004864 filed on Nov. 11, 2016,which claims the benefit of foreign priority of Japanese patentapplication No. 2015-239820 filed on Dec. 9, 2015, the contents all ofwhich are incorporated herein by reference.

BACKGROUND 1. Technical Field

The present disclosure relates to a semiconductor light emitting device,and in particular to a semiconductor light emitting device using a highoutput semiconductor laser, a super luminescent diode, or the like whichemit a visible light having wavelength ranging from blue-violet to red.

2. Description of the Related Art

Recently, development of a high output semiconductor laser device as alight source for providing high intensity lighting has been activelyperformed. For providing a high output from the semiconductor laserdevice, a structure has been examined that disperses, by using aplurality of semiconductor laser elements, load and heat generation ofeach of the semiconductor laser elements to improve reliability of thesemiconductor laser element. A structure of a semiconductor laser devicethat simultaneously drives a plurality of semiconductor laser elementsdisclosed in, for example, Unexamined Japanese Patent Publication No.9-167878 has been examined.

The structure of the conventional semiconductor light emitting devicedisclosed in Unexamined Japanese Patent Publication No. 9-167878 will bedescribed with reference to FIG. 19. The conventional semiconductorlight emitting device is composed of a plurality of semiconductor laserelements in which n-InP clad layer 6, active layer 7, p-InP clad layer8, p-InP current block layer 9, n-InP current block layer 10, p⁺-InP caplayer 11 are laminated on semiconductor insulating substrate 5 in thisorder. The semiconductor laser elements are electrically insulated witheach other by element separation grooves 12 each reaching semiconductorinsulating substrate 5. In the meanwhile, the semiconductor laserelements, which are electrically insulated, has a structure electricallyconnecting, by wire 3, n-side electrode 14 provided on n-InP clad layer6 and p-side electrode 13 provided on p⁺-InP cap layer 11. Thus, aplurality of the semiconductor laser elements are connected in series.

SUMMARY

A semiconductor light emitting device according to the presentdisclosure includes a mount section having an insulating propertyconnected to a heat sink, a plurality of semiconductor laser elementsdisposed on the mount section, and a heat radiation block having aninsulating property disposed on the plurality of semiconductor laserelements. A first wiring made of a metal is formed on an upper surfaceof the mount section, and a second wiring made of a metal is formed on alower surface of the heat radiation block, a part of the second wiringbeing electrically connected to the first wiring. By electricallyconnecting the first wiring and the second wiring to each of theplurality of semiconductor laser elements, the plurality ofsemiconductor laser elements are connected in series, and have a samepolarity with each other at a side that each of the plurality ofsemiconductor laser elements is connected to the first wiring.

According to the semiconductor light emitting device of the presentdisclosure, the plurality of semiconductor laser elements can beelectrically connected in series by using the mount section and the heatradiation block on which the respective metal wirings are formed. Thus,it is possible to avoid concentration of load to one semiconductor laserelement, which is remarkable in a nitride semiconductor light emittingelement. Additionally, by connecting the plurality of semiconductorlaser elements to the mount section at respective sides having the samepolarity with each other, an active layer, which generates large heat,can be disposed so as to be closer to a heat sink in each of theplurality of semiconductor laser elements. Thus, heat generated in theplurality of semiconductor laser elements is efficiently dispersed tothe heat sink. Therefore, it is possible to suppress temperatureincrease of the semiconductor laser elements, so that reliability of thesemiconductor light emitting device can be improved.

The present disclosure can provide a semiconductor light emitting devicehaving high reliability even in high output operation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating a semiconductor light emittingdevice according to a first exemplary embodiment disposed in asemiconductor package;

FIG. 2 is a perspective front side view illustrating the semiconductorlight emitting device according to the first exemplary embodiment;

FIG. 3 is a perspective back side view illustrating the semiconductorlight emitting device according to the first exemplary embodiment;

FIG. 4 is a top view illustrating a mount section according to the firstexemplary embodiment;

FIG. 5 is a bottom view illustrating a heat radiation block according tothe first exemplary embodiment;

FIG. 6 is a front view illustrating a semiconductor laser elementaccording to the first exemplary embodiment;

FIG. 7 is a top view illustrating the semiconductor light emittingdevice according to the first exemplary embodiment;

FIG. 8 is a cross sectional view taken along line VIII-VIII of FIG. 7;

FIG. 9 is a cross sectional view taken along line IX-IX of FIG. 7;

FIG. 10 is a front view illustrating the semiconductor light emittingdevice according to the first exemplary embodiment;

FIG. 11 is a front view illustrating a semiconductor light emittingdevice according to a second exemplary embodiment;

FIG. 12 is a top view illustrating a mount section according to thesecond exemplary embodiment;

FIG. 13 is a bottom view illustrating a heat radiation block accordingto the second exemplary embodiment;

FIG. 14 is a front view illustrating a semiconductor light emittingdevice according to a third exemplary embodiment;

FIG. 15 is a front side perspective view illustrating a semiconductorlight emitting device according to a fourth exemplary embodiment;

FIG. 16 is a back side perspective view illustrating the semiconductorlight emitting device according to the fourth exemplary embodiment;

FIG. 17 is a top view illustrating a mount section according to thefourth exemplary embodiment;

FIG. 18 is a bottom view illustrating a heat radiation block accordingto the fourth exemplary embodiment; and

FIG. 19 is a diagram illustrating a structure of a conventional device.

DETAILED DESCRIPTION OF EMBODIMENT

Before describing exemplary embodiments of the present disclosure,problems in a conventional semiconductor light emitting device will besimply described. There is a problem described below when asemiconductor light emitting device of high output and high reliabilityis provided by using a structure disclosed in Unexamined Japanese PatentPublication No. 9-167878.

First, when insulation between semiconductor laser elements is achievedby an element separation groove as described in Unexamined JapanesePatent Publication No. 9-167878, an insulating substrate needs to beused. Accordingly, for example, in a case of a nitride-basedsemiconductor laser element having a structure that an n-typesemiconductor substrate is used for flowing current to a semiconductorlaser element via the n-type semiconductor substrate, it is difficult toproduce the same structure as the structure disclosed in UnexaminedJapanese Patent Publication No. 9-167878.

Also, since the semiconductor laser elements are connected by a wire,when implementation is performed, a junction up implementation isperformed in which a substrate side is joined to a heat sink.Accordingly, an active layer which mostly generates heat is located awayfrom the heat sink, and thus the temperature of each semiconductor laserelement disadvantageously increases. As a result, reliability of thesemiconductor laser elements decline because of the increase intemperature of the active layer in operation. Furthermore, since thesemiconductor laser elements are connected by a wire, a distance betweenthe semiconductor laser elements increases, so that an interval betweenrespective luminous points disadvantageously become wide.

On the other hand, when the semiconductor laser elements are connectedin parallel, the inventors of the present disclosure have found aproblem described below. By connecting the semiconductor laser elementsin parallel, operating current of the semiconductor laser device becomeshigh. Thus, resistance heating at a joint part of a wire or an electrodeincreases, so that disconnection of the wire or deterioration of theelectrode may disadvantageously occurs.

Furthermore, a p-type semiconductor layer in the nitride-basedsemiconductor laser element generally has large activation energy, sothat its resistance is largely lowered due to increase in carrierdensity associated with temperature rise. Consequently, in the pluralityof semiconductor laser elements connected in parallel, if there isvariation or the like in electrode area or contact resistance,unevenness in temperature occurs between the plurality of semiconductorlaser elements. When unevenness in temperature once occurs between theplurality of semiconductor laser elements, positive feedback that is (1)increase of current, (2) increase of heat generation, (3) lowering ofresistance, and (4) further increase of current, is established in oneof the semiconductor laser elements having a high temperature.Therefore, a load to the one semiconductor laser element accelerativelyincreases.

The present disclosure is conceived to solve the above problem, andprovides a semiconductor light emitting device having high reliabilityalso in high output operation.

Hereinafter, semiconductor light emitting devices according to exemplaryembodiments of the present disclosure will be described with referenceto the drawings.

First Exemplary Embodiment

A structure of a semiconductor light emitting device according to afirst exemplary embodiment will be described with reference to FIG. 1 toFIG. 10. FIG. 1 is a perspective view illustrating the semiconductorlight emitting device according to the first exemplary embodimentdisposed in a semiconductor package. FIG. 2 is a front side perspectiveview illustrating the semiconductor light emitting device according tothe first exemplary embodiment, and FIG. 3 is a back side perspectiveview illustrating the semiconductor light emitting device according tothe first exemplary embodiment. FIG. 4 is a top view illustrating amount section according to the first exemplary embodiment, and FIG. 5 isa bottom view illustrating a heat radiation block according to the firstexemplary embodiment.

As illustrated in FIG. 1, semiconductor light emitting device 120 isinstalled in semiconductor package 110. Semiconductor package 110includes base 113 having a substantially circular plate shape, two leadpins 111 passing completely through base 113, and seat 112 projectingfrom base 113 and having a substantially half cylindrical shape.Semiconductor light emitting device 120 is implemented on seat 112. Leadpin 111 is made of a conductive material such as a metal, andelectrically connected to semiconductor light emitting device 120 via awire or the like, and supplies electric power to semiconductor lightemitting device 120 from an outside of semiconductor package 110. Seat112 is made of a material having high heat conductivity such as a metal,and functions as a heat sink that diffuses heat from semiconductor lightemitting device 120 via an implementation surface with semiconductorlight emitting device 120.

As illustrated in FIG. 2, FIG. 3, semiconductor light emitting device120 has a structure in which two semiconductor laser elements(semiconductor laser element 134 a, semiconductor laser element 134 b)are sandwiched by mount section 130 and heat radiation block 140. Mountsection 130 includes mount substrate 131 made of, for example, aninsulating material such as SiC, AlN, or diamond, and mount wiringsformed on an upper surface of mount substrate 131 and, for example, madeof a material such as Au, Pt, or Ti (mount wiring 132 a, mount wiring132 b). Heat radiation block 140 includes heat radiation block substrate141 made of, for example, an insulating material such as SiC, AlN, ordiamond, heat radiation block wirings (heat radiation block wiring 142a, heat radiation block wiring 142 b described below) formed on a lowersurface of heat radiation block substrate 141 and made of, for example,a metal such as Au, Pt, or Ti, and a heat radiation block wiring (heatradiation block wiring 142 c) formed on the upper surface of heatradiation block substrate 141 and made of, for example, a metal such asAu, Pt, or Ti. Herein, a thickness of mount substrate 131 is preferablynot less than 50 μm and not more than 500 μm, a width of mount substrate131 is preferably not less than 500 μm and not more than 2000 μm, and adepth of mount substrate 131 is preferably not less than 500 μm and notmore than 4000 μm. Also, a thickness of heat radiation block substrate141 is preferably not less than 100 μm and not more than 500 μm, a widthof heat radiation block substrate 141 is preferably not less than 500 μmand not more than 2000 μm, and a depth of heat radiation block substrate141 is preferably not less than 500 μm and not more than 4000 μm. A filmthickness of each of the mount wirings and the heat radiation blockwirings is preferably not less than 50 μm and not more than 300 μm.

Wiring structures on the upper surface of mount section 130 and thelower surface of heat radiation block 140 will be described in detailwith reference to FIG. 4, FIG. 5. As illustrated in FIG. 4, bypatterning a metal layer formed on a surface (the upper surface) ofmount substrate 131, mount wiring 132 a having an L shape and mountwiring 132 b having a rectangular shape are formed. Mount wiring 132 ahas an L shape whose width on a front side is small and whose width on aback side is large. Herein, a lower side in the drawing is the frontside, and an upper side of the drawing is the back side. Mount solderlayer 133 a for joining semiconductor laser element 134 a is formed onthe front side of mount wiring 132 a. Also, mount solder layer 133 c forjoining conductive post 144 (described below) is formed on the back sideof the mount wiring 132 a. Mount solder layer 133 b for joiningsemiconductor laser element 134 b is formed on mount wiring 132 b. Alength in a direction toward the back surface from the front surface ofmount wiring 132 b is shorter than mount wiring 132 a having the Lshape, and a part of mount wiring 132 a is disposed on mount substrate131 on the back side of mount wiring 132 b.

Also, as illustrated in FIG. 5, by patterning a metal layer formed on asurface (the lower surface) of heat radiation block substrate 141, heatradiation block wiring 142 a having a rectangular shape and heatradiation block wiring 142 b having an L shape are formed. Heatradiation block wiring 142 b has an L shape whose width on the frontside is small and whose width on the back side is large. Herein, thelower side in the drawing is the front side, and the upper side of thedrawing is the back side. Heat radiation block solder layer 143 a forjoining semiconductor laser element 134 a is formed on heat radiationblock wiring 142 a. A length in a direction toward the back surface fromthe front surface of heat radiation block wiring 142 a is shorter thanheat radiation block wiring 142 b having the L shape, and a part of heatradiation block wiring 142 b is disposed on heat radiation blocksubstrate 141 on the back side of heat radiation block wiring 142 a.Heat radiation block solder layer 143 b for joining semiconductor laserelement 134 b is formed on the front side of heat radiation block wiring142 b. Also, conductive post 144 is disposed on the back side of heatradiation block wiring 142 b. Conductive post 144 is fixed to heatradiation block wiring 142 b by plating heat radiation block wiring 142b.

As illustrated in FIG. 2, semiconductor laser element 134 a andsemiconductor laser element 134 b are implemented on mount section 130with their laser emission end surfaces being oriented toward the frontside. Specifically, a lower surface of semiconductor laser element 134 ais electrically connected to and mechanically fixed to mount wiring 132a by mount solder layer 133 a. Also, a lower surface of semiconductorlaser element 134 b is electrically connected to and mechanically fixedto mount wiring 132 b by mount solder layer 133 b.

On the upper surface of mount section 130, semiconductor laser element134 a and semiconductor laser element 134 b are disposed on the frontside, and conductive post 144 is disposed on the back side. Asillustrated in FIG. 3, conductive post 144 is electrically connected toand mechanically fixed to mount wiring 132 a extending to the back sideby mount solder layer 133 c. Conductive post 144 may be a block made ofa metal such as CU or Al, or may be a block made of an insulatingmaterial such as AlN or SiC on which a metal is coated.

Heat radiation block 140 is disposed on semiconductor laser element 134a and semiconductor laser element 134 b, and heat radiation block wiring142 a and heat radiation block wiring 142 b are respectively joined withsemiconductor laser element 134 a and semiconductor laser element 134 b.Specifically, an upper surface of semiconductor laser element 134 a iselectrically connected to and mechanically fixed to heat radiation blockwiring 142 a by heat radiation block solder layer 143 a. Also, an uppersurface of semiconductor laser element 134 b is electrically connectedto and mechanically fixed to heat radiation block wiring 142 b by heatradiation block solder layer 143 b.

Also, on the lower surface of heat radiation block 140, semiconductorlaser element 134 a and semiconductor laser element 134 b are disposedon the front side, and conductive post 144 is disposed on the back side.Conductive post 144 is electrically connected to and mechanically fixedto heat radiation block wiring 142 b extending to the back side. Thismakes mount wiring 132 a and heat radiation block wiring 142 b beelectrically connected via conductive post 144.

Also, heat radiation block wiring 142 a is electrically connected toheat radiation block wiring 142 c formed on the upper surface of heatradiation block substrate 141 via conductive via 145 (described below)passing completely through heat radiation block substrate 141.

Next, structures of semiconductor laser element 134 a and semiconductorlaser element 134 b will be described with reference to FIG. 6. FIG. 6is a front view of the semiconductor laser element according to thefirst exemplary embodiment. Herein, semiconductor laser element 134 awill be described as an example.

As illustrated in FIG. 6, semiconductor laser element 134 a includesn-type layer 23 in which n-type clad layer 21 and n-type guide layer 22are sequentially laminated on n-type semiconductor substrate 20, activelayer 24 disposed on n-type layer 23, and p-type layer 28 disposed onactive layer 24 in which p-type guide layer 25, p-type clad layer 26,and p-type contact layer 27 are sequentially laminated. Also, a stripeshaped protrusion is formed in p-type clad layer 26, and a p-typecontact layer 27 is disposed on the protrusion. A ridge is constitutedby the protrusion of p-type clad layer 26 and p-type contact layer 27.An upper surface of p-type clad layer 26 in which no protrusion isformed and side surfaces of the ridge are covered with current blocklayer 29. An opening is formed in current block layer 29 such thatp-type contact layer 27 is exposed, and p-side electrode 30 is in ohmiccontact with p-type contact layer 27 at the ridge by being provided withp-side electrode 30 on the opening. Also, n-side electrode 31 is formedon a lower surface of substrate 20. In this way, semiconductor laserelement 134 a is energized when a voltage is applied between p-sideelectrode 30 and n-side electrode 31, so that laser light is emitted. Inthis context, emission intensity becomes highest in active layer 24 atthe lower side of the ridge due to a light confining effect or the likecaused by the ridge structure. This portion is referred as a luminouspoint. The luminous point can be configured so as to be located not onlyat the center of the semiconductor laser element, but also at a portionshifted on one side by changing the position of the ridge.

When semiconductor laser element 134 a is formed by using anitride-based semiconductor material, GaN or GaN including Al or In canbe used as the above-described semiconductor layer and semiconductorsubstrate. Note that, in order to yield the light confining effect inthe stacking direction of the semiconductor layer, the materials areselected such that a refractive index of active layer 24 becomes higherthan a refractive index of n-type layer 23 and a refractive index ofp-type layer 28. Specifically, n-type semiconductor substrate 20 is madeof GaN. For example, n-type clad layer 21 and n-type guide layer 22 arerespectively made of AlGaN and GaN, and their film thicknesses arerespectively 3 μm, 100 nm. Also, a composition of Al in AlGaN used inn-type clad layer 21 is about 3%. Active layer 24 has a quantum wellstructure in which a well layer of InGaN is surrounded by a barrierlayer having a bandgap larger than that of the well layer, and can emitlight having a desired wavelength by adjusting a composition of In. Athickness of the well layer is preferably not less than 3 nm and notmore than 10 nm. P-type guide layer 25 and p-type clad layer 26 arerespectively made of GaN and AlGaN, and their film thicknesses arerespectively 100 nm, 500 nm. In this context, p-type clad layer 26 maybe constituted by a superlattice of AlGaN and GaN. P-type contact layer27 is made of GaN, and has a p-type dopant concentration higher thanthat of p-type clad layer 26. Also, a film thickness of p-type contactlayer 27 is 5 nm.

In the above-described example, n-type layer 23 is disposed at a sidefacing the substrate, but p-type layer 28 may be disposed at the sidefacing the substrate.

Next, the structure of the semiconductor light emitting device accordingto the first exemplary embodiment will be described in further detailwith reference to FIG. 7 to FIG. 10. FIG. 7 is a top view illustratingthe semiconductor light emitting device according to the first exemplaryembodiment. FIG. 8 is a cross sectional view taken along line VIII-VIIIof FIG. 7, and FIG. 9 is a cross sectional view taken along line IX-IXof FIG. 7.

As illustrated in FIG. 7, heat radiation block substrate 141 is smallerthan mount substrate 131 in a plan view, and a part of mount wiring 132a and a part of mount wiring 132 b are not covered with heat radiationblock substrate 141. This makes it possible to connect a wire to thepart of mount wiring 132 a or the part of mount wiring 132 b exposedfrom heat radiation block substrate 141 for electrical connection.Furthermore, this makes it possible to connect a wire to heat radiationblock wiring 142 c disposed on the upper surface of heat radiation blocksubstrate 141 for electrical connection. Hereinafter, cross sectionalstructures of semiconductor light emitting device 120 at a part at whichsemiconductor laser element 134 a is disposed and at a part at whichsemiconductor laser element 134 b is disposed will be described withreference to FIG. 8, FIG. 9, respectively.

As illustrated in FIG. 8, conductive via 145 is formed in heat radiationblock substrate 141 and is disposed on semiconductor laser element 134 aso as to penetrate through heat radiation block substrate 141.Conductive via 145 is constituted by a conductive material such astungsten or copper which is embedded in a through hole formed in heatradiation block substrate 141. An upper surface of conductive via 145 iselectrically connected to heat radiation block wiring 142 c, and a lowersurface of conductive via 145 is electrically connected to heatradiation block wiring 142 a. Thus, heat radiation block wiring 142 cand heat radiation block wiring 142 a are electrically connected viaconductive via 145. As illustrated in the drawing, heat radiation blockwiring 142 c and heat radiation block wiring 142 a may be connected byusing a plurality of conductive vias 145.

Heat radiation block wiring 142 a is joined to an electrode at the upperside of semiconductor laser element 134 a via heat radiation blocksolder layer 143 a. Also, an electrode at the lower side ofsemiconductor laser element 134 a is joined to mount wiring 132 a viamount solder layer 133 a. Thus, by applying a voltage between mountwiring 132 a and heat radiation block wiring 142 c that is connected toheat radiation block wiring 142 a, current is supplied to semiconductorlaser element 134 a, so that it is possible for semiconductor laserelement 134 a to emit laser light.

Also, as illustrated in FIG. 9, heat radiation block wiring 142 b thatis disposed on semiconductor laser element 134 b and in the lowersurface of heat radiation block substrate 141 is joined to an electrodeat the upper side of semiconductor laser element 134 b via heatradiation block solder layer 143 b. Furthermore, an electrode at thelower side of semiconductor laser element 134 b is joined to mountwiring 132 b via mount solder layer 133 b. Thus, by applying a voltagebetween heat radiation block wiring 142 b and mount wiring 132 b,current is supplied to semiconductor laser element 134 b, so that it ispossible for semiconductor laser element 134 b to emit laser light.

Furthermore, as illustrated in FIG. 8, FIG. 9, mount wiring 132 a andheat radiation block wiring 142 b are electrically connected viaconductive post 144, so that semiconductor laser element 134 a andsemiconductor laser element 134 b are connected in series. That is, byapplying a voltage between heat radiation block wiring 142 c and mountwiring 132 b, it is possible to supply current to both semiconductorlaser element 134 a and semiconductor laser element 134 b.

FIG. 10 is a front view illustrating the semiconductor light emittingdevice according to the first exemplary embodiment. As illustrated inFIG. 10, both semiconductor laser element 134 a and semiconductor laserelement 134 b are joined to mount wiring 132 a and mount wiring 132 b ofmount substrate 131, respectively, at a side of p-type layer 28(junction down type implementation). Herein, each of semiconductor laserelement 134 a and semiconductor laser element 134 b has n-type substrate20 and the semiconductor layer including active layer 24 (n-type layer23, active layer 24, and p-type layer 28 disposed on n-type substrate 20in this order) formed on n-type substrate 20 as illustrated in FIG. 6.As described above, semiconductor laser element 134 a is joined withmount wiring 132 a at a side of the semiconductor layer, andsemiconductor laser element 134 b is joined with mount wiring 132 b at aside of the semiconductor layer. Therefore, in a case of semiconductorlaser element 134 a and semiconductor laser element 134 b using n-typesubstrate 20, there is not n-type substrate 20 between active layer 24and p-side electrode 30, so that a distance from active layer 24 tomount substrate 131 is short. Thus, a heat dissipation path fordissipating heat generated in active layer 24 to semiconductor package110, which is a heatsink, via mount substrate 131 can be short, so thatit is possible to suppress temperature increase of semiconductor laserelement 134 a and semiconductor laser element 134 b.

Furthermore, in order to make luminous point 139 a of semiconductorlaser element 134 a and luminous point 139 b of semiconductor laserelement 134 b locate close to each other, positions of the respectiveridges are changed to locate close to each other. Thus, the intervalbetween the luminous points can be not more than 100 μm, so that it ispossible to improve combining efficiency with an optical system.

As described above, in the semiconductor light emitting device accordingto the present exemplary embodiment, by applying a voltage between mountwiring 132 b and heat radiation block wiring 142 c, current flows frommount wiring 132 b to heat radiation block wiring 142 c throughsemiconductor laser element 134 b, heat radiation block wiring 142 b,conductive post 144, mount wiring 132 a, semiconductor laser element 134a, heat radiation block wiring 142 a, and conductive via 145 in thisorder. That is, the semiconductor light emitting device of the exemplaryembodiment makes it possible to flow current in the two semiconductorlight emitting elements (semiconductor light emitting element 134 a andsemiconductor light emitting element 134 b) in series as well as disposethe two semiconductor light emitting elements so as to locate theelectrodes having the same polarity (P-type) of the respectivesemiconductor laser elements near the heat sink.

As described above, the problem that a load is concentrated in onesemiconductor light emitting device due to connecting a plurality ofsemiconductor laser elements in parallel can be solved. And thusreliability of the semiconductor light emitting device of high outputusing a plurality of semiconductor laser elements can be improved.

Furthermore, since the two semiconductor laser elements (semiconductorlaser element 134 a, semiconductor laser element 134 b) are alsoconnected to heat radiation block 140, heat can be radiated not only tomount section 130 but also to heat radiation block 140. Furthermore,since the heat transmitted to heat radiation block 140 can be radiatedto mount section 130 via conductive post 144, temperature increase ofthe semiconductor laser elements can be drastically suppressed. Thus, itis possible to improve reliability of the semiconductor light emittingdevice.

Furthermore, since luminous point 139 a and luminous point 139 b can bedisposed in a plane parallel to the implementation surface ofsemiconductor package 110 and semiconductor light emitting device 120,and the interval between the luminous points can be shortened, it ispossible to improve coupling efficiency with the optical system.Therefore, it is possible to secure required light quantity with smallerinput power, so that temperature increase of the semiconductor laserelements can be suppressed. Thus, it is possible to improve reliabilityof the semiconductor light emitting device. As descried above, thesemiconductor light emitting device having high reliability even inhigh-power operation can be provided.

Second Exemplary Embodiment

A structure of a semiconductor light emitting device according to asecond exemplary embodiment will be described with reference to FIG. 11to FIG. 13. FIG. 11 is a front view illustrating the semiconductor lightemitting device according to the second exemplary embodiment. FIG. 12 isa top view illustrating a mount section according to the secondexemplary embodiment, and FIG. 13 is a bottom view illustrating a heatradiation block according to the second exemplary embodiment. Note thatthe structure same as that of the first exemplary embodiment will not bedescribed, and a structure different from that of the first exemplaryembodiment will be mainly described.

As illustrated in FIG. 11, in semiconductor light emitting device 220 ofthe present exemplary embodiment, mount groove 251 is provided betweenmount wiring 232 a and mount wiring 232 b of mount section 230.Furthermore, heat radiation block groove 252 is provided between heatradiation block wiring 242 a and heat radiation block wiring 242 b ofheat radiation block 240. Other structure is the same as that ofsemiconductor light emitting device 120 of the first exemplaryembodiment.

As described in FIG. 12, mount groove 251 has a shape bent in an L shapealong an outline of mount wiring 232 a having an L shape. In otherwords, mount groove 251 is entirely formed over a gap between mountwiring 232 a and mount wiring 232 b.

Also, as illustrated in FIG. 13, heat radiation block groove 252 has ashape bent in an L shape along an outline of heat radiation block wiring242 b having an L shape. In other words, heat radiation block groove 252is entirely formed over a gap between heat radiation block wiring 242 aand heat radiation block wiring 242 b.

Herewith, in semiconductor light emitting device 220 of the presentexemplary embodiment, even when mount solder layer 233 a for joiningsemiconductor laser element 234 a to mount section 230 is widened toprotrude sideways, mount solder layer 233 a is suppressed to be incontact with mount semiconductor layer 232 b by mount groove 251provided between mount wiring 232 a and mount wiring 232 b. Likewise,mount solder layer 233 b is suppressed to be in contact with mountwiring 232 a by mount groove 251.

Also, even when heat radiation block solder layer 243 a for joiningsemiconductor laser element 234 a to heat radiation block 240 is widenedto protrude sideways, heat radiation block solder layer 243 a issuppressed to be in contact with heat radiation block wiring 242 b byheat radiation block groove 252 provided between heat radiation blockwiring 242 a and heat radiation block wiring 242 b. Likewise, heatradiation block solder layer 243 b is suppressed to be in contact withheat radiation block wiring 242 a by heat radiation block groove 252.

As described above, leakage current due to an electrical short circuitbetween semiconductor laser element 234 a and semiconductor laserelement 234 b can be suppressed. Thus, it is possible to improvereliability of the semiconductor light emitting device and yield duringmanufacture of the semiconductor light emitting device. Otheradvantageous effects are the same as those of the first exemplifiedembodiment.

Third Exemplary Embodiment

A structure of a semiconductor light emitting device according to athird exemplary embodiment will be described with reference to FIG. 14.FIG. 14 is a front view illustrating the semiconductor light emittingdevice according to the third exemplary embodiment. Note that thestructure same as that of the first exemplary embodiment will not bedescribed, and a structure different from that of the first exemplaryembodiment will be mainly described.

As illustrated in FIG. 14, in semiconductor light emitting device 320 ofthe present exemplary embodiment, mount protrusion 351 is providedbetween mount wiring 332 a and mount wiring 332 b of mount section 330.Similar to mount grove 251 in semiconductor light emitting device 220 ofthe second exemplary embodiment, mount protrusion 351 has a shape bentin an L shape (not shown) along an outline of mount wiring 332 a havingan L shape. In other words, mount protrusion 351 is entirely formed overa gap between mount wiring 332 a and mount wiring 332 b.

Furthermore, a height of mount protrusion 351 is set to be substantiallyequal to a value that is a sum of a height of mount wiring 332 a and aheight of mount solder layer 333 a when semiconductor laser element 334a is implemented on mount section 330, or a sum of a height of mountwiring 332 b and a height of mount solder layer 333 b when semiconductorlaser element 334 b is implemented on mount section 330. Also, a widthof mount protrusion 351 is larger than a gap between semiconductor laserelement 334 a and semiconductor laser element 334 b. And a part ofsemiconductor laser element 334 a and a part of semiconductor laserelement 334 b are placed on mount protrusion 351.

Also, heat radiation block protrusion 352 is provided between heatradiation block wiring 342 a and heat radiation block wiring 342 b ofheat radiation block 340. Heat radiation block protrusion 352 has ashape bent in an L shape along an outline of heat radiation block wiring342 b having an L shape similar to heat radiation block groove 252 insemiconductor light emitting device 220 of the second exemplaryembodiment. In other words, heat radiation block protrusion 352 isentirely formed over a gap between heat radiation block wiring 342 a andheat radiation block wiring 342 b.

Furthermore, a height of heat radiation block protrusion 352 is set tobe substantially equal to a value that is a sum of a height of heatradiation block wiring 342 a and a height of heat radiation block solderlayer 343 a when heat radiation block 340 is implemented onsemiconductor laser element 334 a, or a sum of a height of heatradiation block wring 342 b and a height of heat radiation block solderlayer 343 b when heat radiation block 340 is implemented onsemiconductor laser element 334 b. Also, a width of heat radiation blockprotrusion 352 is larger than a gap between semiconductor laser element334 a and semiconductor laser element 334 b. And heat radiation blockprotrusion 352 is placed on a part of semiconductor laser element 334 aand a part of semiconductor laser element 334 b. Note that otherstructures are the same as those of semiconductor light emitting device120 of the first exemplary embodiment.

Herewith, in semiconductor light emitting device 320 of the presentexemplary embodiment, even when mount solder layer 333 a for joiningsemiconductor laser element 334 a to mount section 330 is widened toprotrude sideways, mount solder layer 333 a is suppressed to be incontact with mount wiring 332 b by mount protrusion 351 provided betweenmount wiring 332 a and mount wiring 332 b. Likewise, mount solder layer333 b is suppressed to be in contact with mount wiring 332 a by mountprotrusion 351.

Also, even when heat radiation block solder layer 343 a for joiningsemiconductor laser element 334 a to heat radiation block 340 is widenedto protrude sideways, heat radiation block solder layer 343 a issuppressed to be in contact with heat radiation block wiring 342 b byheat radiation block protrusion 352 provided between heat radiationblock wiring 342 a and heat radiation block wiring 342 b. Likewise, heatradiation block solder layer 343 b is suppressed to be in contact withheat radiation block wiring 342 a by heat radiation block protrusion352.

As described above, leakage current due to an electrical short circuitbetween semiconductor laser element 234 a and semiconductor laserelement 234 b can be suppressed. Thus it is possible to improvereliability of the semiconductor light emitting device and yield duringmanufacture of the semiconductor light emitting device.

Also, since a part of semiconductor laser element 334 a and a part ofsemiconductor laser element 334 b are placed on mount protrusion 351,implementation can be performed while keeping a constant distance from abottom surface of mount section 330 to luminous point 339 a ofsemiconductor laser element 334 a and luminous point 339 b ofsemiconductor laser element 334 b. Therefore, it is possible to reducepositional variation of the luminous points with respect tosemiconductor package 110, thus it is easy to design an optical system.Other advantageous effects are the same as those of the firstexemplified embodiment.

Fourth Exemplary Embodiment

A structure of a semiconductor light emitting device according to afourth exemplary embodiment will be described with reference to FIG. 15to FIG. 18. FIG. 15 is a front side perspective view illustrating thesemiconductor light emitting device according to the fourth exemplaryembodiment, and FIG. 16 is a back side perspective view illustrating thesemiconductor light emitting device according to the fourth exemplaryembodiment. FIG. 17 is a top view illustrating a mount section accordingto the fourth exemplary embodiment, and

FIG. 18 is a bottom view illustrating a heat radiation block accordingto the fourth exemplary embodiment. Note that the structure same as thatin the first exemplary embodiment will not be described, and a structuredifferent from that of the first exemplary embodiment will be mainlydescribed. As illustrated in FIG. 15, semiconductor light emittingdevice 420 according to the present exemplary embodiment has a structurein which three semiconductor laser elements (semiconductor laser element434 a, semiconductor laser element 434 b, and semiconductor laserelement 434 c) are sandwiched between mount section 430 and heatradiation block 440. Mount section 430 has mount substrate 431 and mountwirings (mount wiring 432 a, mount wiring 432 b, and mount wiring 432 c)formed on an upper surface of mount substrate 431. Furthermore, heatradiation block 440 has heat radiation block substrate 441, heatradiation block wirings (heat radiation block wiring 442 a, heatradiation block wiring 442 b, and heat radiation block wiring 442 c tobe described below) formed on a lower surface of heat radiation blocksubstrate 441, and a heat radiation block wiring (heat radiation blockwiring 442 d) formed on an upper surface of heat radiation blocksubstrate 441. The materials of mount substrate 431, the mount wirings,heat radiation block substrate 441, and the heat radiation block wiringsare the same as those in the first exemplary embodiment. Note that otherstructures are the same as those of semiconductor light emitting device120 of the first exemplary embodiment.

A wiring structure on upper surface of mount section 430 and lowersurface of heat radiation block 440 will be described in detail withreference to FIG. 17 and FIG. 18, respectively. As illustrated in FIG.17, by patterning a metal layer formed on a surface (upper surface) ofmount substrate 431, mount wiring 432 a having an L shape, mount wiring432 c having a rectangular shape, and mount wiring 432 b located betweenmount wiring 432 a and mount wiring 432 c are formed. Mount wiring 432 bhas an L shape in which a part thereof is cut out. Mount wiring 432 ahas an L shape whose width at the front side is small and whose width atthe back side is large. Also, mount wiring 432 b has an L shape whosewidth at the front side is small and whose width at the back side islarge, one corner of which is cut out. Herein, the lower side in thedrawing is the front side, and the upper side of the drawing is the backside. Mount solder layer 433 a for joining semiconductor laser element434 a is formed on mount wiring 432 a at the front side. Also, mountsolder layer 433 d for joining conductive post 444 a (described below)is formed on mount wiring 432 a at the back side. Mount solder layer 433b for joining semiconductor laser element 434 b is formed on mountwiring 432 b at the front side. Also, mount solder layer 433 e forjoining conductive post 444 b (described below) is formed on mountwiring 432 b at the back side. Mount solder layer 433 c for joiningsemiconductor laser element 434 c is formed on mount wiring 432 c.

Furthermore, as illustrated in FIG. 18, by patterning a metal layerformed on a surface (lower surface) of heat radiation block substrate441, heat radiation block wiring 442 a having a rectangular shape, heatradiation block wiring 442 c having an L shape, and heat radiation blockwiring 442 b located between heat radiation block wiring 442 a and heatradiation block wiring 442 c are formed. Heat radiation block wiring 442b has an L shape in which a part thereof is cut out. Heat radiationblock wiring 442 c has an L shape whose width at the front side is smalland whose width at the back side is large. Also, heat radiation blockwiring 442 b has an L whose width at the front side is small and whosewidth at the back side is large, one corner of which is cut out. Herein,the lower side in the drawing is the front side, and the upper side inthe drawing is the back side. Heat radiation block solder layer 443 cfor joining semiconductor laser element 434 c is formed on heatradiation block wiring 442 c at the front side. Also, conductive post444 b is disposed on heat radiation block wiring 442 c at the back side.Heat radiation block solder layer 443 b for joining semiconductor laserelement 434 b is formed on heat radiation block wiring 442 b at thefront side. Also, conductive post 444 a is disposed on heat radiationblock wiring 442 b at the back side. Heat radiation block solder layer443 a for joining semiconductor laser element 434 a is formed on heatradiation block wiring 442 a.

As illustrated in FIG. 15, semiconductor laser element 434 a,semiconductor laser element 434 b, and semiconductor laser element 434 care implemented on mount section 430 with their laser emission endsurfaces being oriented toward the front side. Specifically, the lowersurface of semiconductor laser element 434 a is electrically connectedto and mechanically fixed to mount wiring 432 a by mount solder layer433 a. Also, the lower surface of semiconductor laser element 434 b iselectrically connected to and mechanically fixed to mount wiring 432 bby mount solder layer 433 b. Also, the lower surface of semiconductorlaser element 434 c is electrically connected to and mechanically fixedto mount wiring 432 c by mount solder layer 433 c.

On the upper surface of mount section 430, semiconductor laser element434 a, semiconductor laser element 434 b, and semiconductor laserelement 434 c are disposed at the front side, and conductive post 444 aand conductive post 444 b are disposed at the back side. As illustratedin FIG. 16, by mount solder layer 433 d, conductive post 444 a iselectrically connected to and mechanically fixed to mount wiring 432 a,which is extending to the back side. Also, by mount solder layer 433 e,conductive post 444 b is electrically connected to and mechanicallyfixed to mount wiring 432 b, which is extending to the back side. Thematerial of conductive post 444 a and conductive post 444 b are the sameas that in the first exemplary embodiment.

Heat radiation block 440 is disposed on semiconductor laser element 434a, semiconductor laser element 434 b, and semiconductor laser element434 c. And heat radiation block wiring 442 a, heat radiation blockwiring 442 b, and heat radiation block wiring 442 c are respectivelyjoined with semiconductor laser element 434 a, semiconductor laserelement 434 b, and semiconductor laser element 434 c. Specifically, theupper surface of semiconductor laser element 434 a is electricallyconnected to and mechanically fixed to heat radiation block wiring 442 aby heat radiation block solder layer 443 a. Also, the upper surface ofsemiconductor laser element 434 b is electrically connected to andmechanically fixed to heat radiation block wiring 442 b by heatradiation block solder layer 443 b. Also, the upper surface ofsemiconductor laser element 434 c is electrically connected to andmechanically fixed to heat radiation block wiring 442 c by heatradiation block solder layer 443 c.

On the lower surface of heat radiation block 440, semiconductor laserelement 434 a, semiconductor laser element 434 b, and semiconductorlaser element 434 c are disposed at the front side, and conductive post444 a and conductive post 444 b are disposed at the back side.Conductive post 444 a is electrically connected to and mechanicallyfixed to heat radiation block wiring 442 b, which is extending to theback side. Thus, mount wiring 432 a and heat radiation block wiring 442b are electrically connected via conductive post 444 a. Also, conductivepost 444 b is electrically connected to and mechanically fixed to heatradiation block wiring 442 c, which is extending to the back side. Thus,mount wiring 432 b and heat radiation block wiring 442 c areelectrically connected via conductive post 444 b.

Furthermore, heat radiation block wiring 442 a is electrically connectedto heat radiation block wiring 442 d formed on the upper surface of heatradiation block substrate 441 via a conductive via (not shown)penetrating through heat radiation block substrate 441. Note that astructure of the conductive via is the same as that in the firstexemplary embodiment.

Also, the structure of each of semiconductor laser element 434 a,semiconductor laser element 434 b, and semiconductor laser element 434 cis the same as that in the first exemplary embodiment.

As described above, in semiconductor light emitting device 420 of theexemplary embodiment, it is possible to connect the three semiconductorlaser elements (semiconductor laser element 434 a, semiconductor laserelement 434 b, and semiconductor laser element 434 c) in series in astate where the electrodes having the same polarity (p-type) of thethree semiconductor laser elements are joined to mount section 430similar to the first exemplary embodiment. That is, by applying avoltage between mount wiring 432 c and heat radiation block wiring 442d, it is possible to simultaneously emit laser light from the threesemiconductor laser elements (semiconductor laser element 434 a,semiconductor laser element 434 b, and semiconductor laser element 434c). Other advantageous effects are the same as those of the firstexemplified embodiment.

As described above, the content of the present disclosure is describedusing the first to fourth exemplary embodiments, but the presentdisclosure is not limited to the exemplary embodiments. For example, inthe above-described exemplary embodiments, the heat radiation blockwirings respectively formed on the upper surface and the lower surfaceof the heat radiation block substrate are electrically connected to eachother by using the conductive via penetrating through the heat radiationblock substrate. The heat radiation block wirings on the upper surfaceand the lower surface, however, may be electrically connected to eachother by a conductive film formed on a side surface of the heatradiation block substrate instead of the conductive via.

Furthermore, although the above-described exemplary embodimentillustrates a case where a number of semiconductor laser elementsconnected in series is two or three, four or more semiconductor laserelements can be connected in series by the same structure.

The present disclosure can be applied to a high output light source orthe like used for an industrial lighting device such as a vehiclelighting device, a spot lighting device in a factory or a gym, or a shoplighting device.

What is claimed is:
 1. A semiconductor laser device comprising: a mountsection; a first wiring and a second wiring connected to an uppersurface of the mount section; a first semiconductor laser element havingan electrode at an upper side, an electrode at a lower side and a ridge;the electrode at the lower side of the first semiconductor laser elementis joined to an upper surface of the first wiring; and a third wiringjoined to the electrode at the upper surface of the first semiconductorlaser element, wherein: the first semiconductor laser element has afront side which is a laser emission end surface, a back side oppositeto the front side and sides between the front side and the back side,the second wiring includes an L shape portion in plan view, and the Lshape potion has a portion opposite to the side of the firstsemiconductor laser element and a portion opposite to the back side ofthe first semiconductor laser element.
 2. The semiconductor laser deviceaccording to claim 1, wherein a width of the second wiring on the backside is larger than the front side along a direction perpendicular to alongitudinal direction of the first semiconductor laser element.
 3. Thesemiconductor laser device according to claim 2, further comprising asecond semiconductor laser element having an electrode at an upper side,an electrode at a lower side and a ridge, wherein the third wiring iselectrically connected to the electrode at the lower side of the secondsemiconductor laser element.
 4. The semiconductor laser device accordingto claim 3, wherein the first semiconductor laser element and the secondsemiconductor laser element are connected in series.
 5. Thesemiconductor laser device according to claim 4, wherein each of sidesclose to the mount section of the first semiconductor laser element andthe second semiconductor laser element has a same polarity.
 6. Thesemiconductor laser device according to claim 5, wherein the each of thesides has a p-type layer.
 7. A semiconductor laser device comprising: amount section; a first wiring and a second wiring connected to an uppersurface of the mount section; a first semiconductor laser element havingan electrode at an upper side, an electrode at a lower side and a ridge;the electrode at the lower side of the first semiconductor laser elementis soldered to an upper surface of the first wiring; and a third wiringsoldered to the electrode at the upper surface of the firstsemiconductor laser element, wherein: the first semiconductor laserelement has a front side which is a laser emission end surface, a backside opposite to the front side and sides between the front side and theback side, the second wiring includes an L shape in plan view, and the Lshape portion has a portion opposite to the side of the firstsemiconductor laser element and a portion opposite to the back side ofthe first semiconductor laser element.
 8. The semiconductor laser deviceaccording to claim 7, wherein a width of the second wiring on the backside is larger than the front side along a direction perpendicular to alongitudinal direction of the first semiconductor laser element.
 9. Thesemiconductor laser device according to claim 8, further comprising asecond semiconductor laser element having an electrode at an upper side,an electrode at a lower side and a ridge, wherein the third wiring iselectrically connected to the electrode at the lower side of the secondsemiconductor laser element.
 10. The semiconductor laser deviceaccording to claim 9, wherein the first semiconductor laser element andthe second semiconductor laser element are connected in series.
 11. Thesemiconductor laser device according to claim 10, wherein each of sidesclose to the mount section of the first semiconductor laser element andthe second semiconductor laser element has a same polarity.
 12. Thesemiconductor laser device according to claim 11, wherein the each ofthe sides has a p-type layer.